When measuring signals, interferences, such as crosstalk and noise, are influencing and disturbing the signal to be measured. This leads to a loss of quality of the measurement.
FIG. 1 shows a prior art example of a measurement setup. A device under test comprises two transistors 2, 4. The gate-source voltage of the first transistor 2 shall be measured using a differential probe 6 connected to the gate and the source of the first transistor 2.
However, a large, periodic voltage across the second transistor 4 interferes with the measurement because real differential probes cannot completely compensate fast changing voltages with large amplitudes.
Thus, the signal M measured by the differential probe 6 comprises the signal to be measured S and the signal causing interference I convoluted with a transfer function H as illustrated in FIG. 1.
The transfer function H represents the coupling between the signal to be measured S or the signal line carrying the signal to be measured S and the signal causing interference I. This disturbed signal is measured at a measuring device 8, for instance an oscilloscope, being connected to the probe 6. Besides the shown example, interference can also arise from signal lines running very close to each other and other known causes.
As the interference deteriorates the measurement quality, attempts are made to reduce the interference completely.
It is known in the prior art to provide a shielding for the measurement line in order to prevent crosstalks or any other coupling between the signal line and a potential source of interference.
However, interference cannot be reduced to zero in this way. Further, the costs increase due to the additional hardware required in order to minimize the occurring interferences.